1. Field of the Invention
The invention relates to a ADPCM (Adaptive Differential Pulse Code Modulation) decoder which conforms with the ITU-T Recommendation G.726.
2. Related Background Arts
A communication system which conforms with the ITU-T Recommendation G.726 ADPCM has been spread as a compression system of an audio signal. According to an error correction system of a transmission error in the communication system, a transmitter inserts a check bit into a transmission frame and transmits the resultant transmission frame. A system such that when a receiver receives the transmission frame, it extracts the check bit and discriminates the presence or absence of the transmission error in a transmission system. When the receiver detects the transmission error, it corrects the transmission frame on the basis of a predetermined error correction system and inputs the error-corrected transmission frame to a decoder (for example, refer to the abstract of JP-A-7-221718), a system such that when the receiver detects the transmission error, it replaces the transmission frame in accordance with a predetermined procedure (for example, refer to the abstract of JP-A-8-223126), or the like has been put into practical use.
As described above, according to the conventional error correction system of the transmission error, when the receiver detects the transmission error by using the check bit, the error correction is executed before the transmission frame is inputted to the ADPCM decoder. Therefore, since the error correction of the transmission error is executed on the basis of the predetermined error correction system at a place that is different from that of the ADPCM decoder, a problem to be solved such that its processes are complicated and hardware to execute the processes also increases remains.